Heat Utilization in ORC Systems

ABSTRACT

Apparatus, systems and methods are provided for the improved use of waste heat recovery systems which utilize the organic Rankine cycle (ORC) to generate mechanical and/or electric power from heat sources generating power from biofuel such as biogas produced during the anaerobic digestion process. Waste heat energy obtained from heat source(s) is provided to one or more ORC system(s) which may be operatively coupled to electric generator(s). A heat coupling subsystem provides the requisite condensation of ORC working fluid by transferring heat from ORC working fluid to another process or system, such as anaerobic digester tank(s), to provide heat energy that enhances the production of fuel for the prime mover(s) without requiring the consumption of additional energy for that purpose.

RELATED APPLICATIONS

This application is a Continuation and claims domestic benefit ofco-owned pending U.S. Nonprovisional patent application Ser. No.13/758,941, filed Feb. 4, 2013 and entitled “Improved Heat Utilizationin ORC Systems”, which in turn claimed benefit of co-owned U.S.Provisional Patent Application 61/594,168 entitled “Improved HeatUtilization in ORC Systems”, filed Feb. 2, 2012, both of whichapplications are incorporated herein by reference in their entiretiesfor all useful purposes. In the event of inconsistency between anythingstated in this specification and anything incorporated by reference inthis specification, this specification shall govern.

FIELD OF INVENTION

The present invention relates to the apparatus, systems, and methods ofutilizing organic Rankine cycle systems for the generation of power fromwaste heat sources.

BACKGROUND

Many physical processes are inherently exothermic, meaning that someenergy previously present in another form is converted to heat by theprocess. While the generation of heat energy may be the desired outcomeof such a process, as with a boiler installed to provide radiant heat toa building using a network of conduits which circulate hot water toradiators or a furnace used for the smelting of metals, in many otherinstances unwanted heat is produced as a byproduct of the primaryprocess. One such example is that of the internal combustion ermine ofan automobile where the primary function is to provide motive force butwhere the generation of significant unwanted heat is unavoidable. Evenin those processes where the generation of heat energy is desired, somedegree of residual heat unavoidably escapes or remains which can bemanaged and/or dissipated. Whether generated intentionally orincidentally, this residual, or waste, heat represents that portion ofthe input energy which was not successfully applied to the primaryfunction of the process in question. This wasted enemy detracts from theperformance, efficiency, and cost effectiveness of the system.

With respect to the internal combustion engine common to mostautomobiles, considerable waste heat energy is generated by thecombustion of fuel and the friction of moving parts within the engine.Automobiles are equipped with extensive systems that transfer the heatenergy away from the source locations and distribute that enemythroughout a closed-loop recirculating system, which usually employs awater-based coolant medium flowing under pressure through jackets withinthe engine coupled to a radiator across which the imposition of forcedair dissipates a portion of the undesired heat energy into theenvironment. This cooling system is managed to permit the engine tooperate at the desired temperature, removing some but not all of theheat energy generated by the engine.

As a secondary function, a portion of the heat energy captured by theengine cooling system may be used to indirectly provide warm air asdesired to the passenger compartment for the operator's comfort. Thisrecaptured and re-tasked portion of the waste heat energy generated as abyproduct of the engine's primary function represents one familiarexample of the beneficial use of waste heat.

Very large internal combustion engines are widely used in heavy industryin numerous applications. For example, General Electric's Jenbacher gasengine division produces a full range of engines with output powercapabilities ranging from 250 kW to over 4,000 kW (by comparison, atypical mid-class automobile engine produces about 150 kW of usableoutput power). The Jenbacher engines can be powered by a variety offuels, including but not limited to natural gas, biogas (such asprovided by anaerobic digestion), and other combustible gasses includingthose from landfills, sewage, and coal mines. One common use of lamecombustion engines, such as the Jenbacher model 312 and 316 engines, isto co-locate them at a biogas generation facility. This consolidates, atone location, (i) the elimination of biodegradable waste products thatrelease chemical energy in the form of combustible biogas and (ii) thecapture and combustion of the biogas in large combustion engines togenerate useful power.

These engines are frequently employed to drive electric powergenerators, converting the rotational mechanical energy from the energyof combustion into electrical energy. One such example of an anaerobicdigestion system specifically designed for the generation of electricpower from biogas is offered by Harvest Power of Waltham, Mass.

In operation, these engines generate tremendous amounts of waste heatenergy that has historically been dissipated into the environment. Inthe case of the combined Jenbacher model 316 engine and generator systemwith a maximum electric power output of approximately 835 kW,approximately 460 kW of heat energy is lost in the exhaust gas (at anapproximate temperature of 950° F.) and approximately another 570 kW islost in the cooling system (with a typical jacket water coolanttemperature of approximately 200° F.). From this data, it can be seenthat less than half of the system's power output is in the desired form(in this case, electric power output from the system generator). Unlessrecaptured and repurposed, however, the portion of the input energyconverted to heat is lost. In many prior art systems, this heat energyis lost and additional energy is required to cool the recirculatingjacket water. The heat from exhaust gas generally escapes into theatmosphere, and the recirculating jacket water is cooled by an outboardapparatus (such as by large external condensing radiators driven byforced air sources), which consume additional electric power to functionand further reduce the efficiency of the system.

Additionally, the dissipation of this waste heat energy into theenvironment can have deleterious effects. Localized heating mayadversely affect local fauna and flora and can require additional power,either generated locally or purchased commercially, to provideadditional or specialized cooling. Further, the noise generated byforced air cooling of the jacket water heat radiators can haveundesirable secondary effects.

With regard to engines fueled by anaerobic-digestion-generated biofuel,a variety of techniques, including the use of electrical heatingsystems, have been employed to provide heat energy to anaerobicdigestion processes necessary for relatively efficient generation ofbiogas by heated microorganisms. These systems consume considerableenergy and therefore have an attendant cost of operation andmaintenance. For example, the anaerobic digester heating systems offeredby Walker Process Equipment of Aurora, Ill. produce hot water in excessof 160° F. using electric power with boilers fueled by biogas, naturalgas, or fuel oil as input energy. In addition to the energy consumed toprovide this hot water, additional electric energy must be consumed tomanage the waste heat from this apparatus.

Waste heat energy systems employing the organic Rankine cycle (ORC)system have been developed and employed to recapture waste heat fromsources such as the Jenbacher 312 and 316 combustion engines. Onetypical prior art ORC system for electric power generation from wasteheat is depicted in FIG. 1. Heat exchanger 101 receives a flow of a heatexchange medium in a closed loop system heated by energy from a largeinternal combustion engine at port 106.

For example, this heat energy may be directly supplied from thecombustion engine via the jacket water heated when cooling thecombustion engine, or it may be coupled to the ORC system via anintermediate heat exchanger system installed proximate to the source ofexhaust gas of one or more combustion engines. In either event, heatedmatter from the combustion engine or heat exchanger is pumped to port106 or its dedicated equivalent. The heated matter flows through heatexchanger 101 and exits at port 107 after transferring a portion of itslatent heat energy to the separate but thermally coupled closed loop ORCsystem which typically employs an organic refrigerant as a workingfluid. Under pressure from the system pump 105, the heated workingfluid, predominantly in a gaseous state, is applied to the input port ofexpander 102, which may be a positive displacement machine of variousconfigurations, including but not limited to a twin screw expander or aturbine. Here, the heated and pressurized working fluid is allowed toexpand within the device, and such expansion produces rotational kineticenergy that is operatively coupled to drive electrical generator 103 andproduce electric power which then may be delivered to a local, isolatedpower grid or the commercial power grid. The expanded working fluid atthe output port of the expander, which typically is a mixture of liquidand gaseous working fluid, is then delivered to condenser subsystem 104where it is cooled until it has returned to its fully liquid state.

The condenser subsystem sometimes includes an array of air-coolerradiators or another system of equivalent performance through which theworking fluid is circulated until it reaches the desired temperature andstate, at which point it is applied to the input of system pump 105.System pump 105 provides the motive force to pressurize the entiresystem and supply the liquid working fluid to heat exchanger 101, whereit once again is heated by the energy supplied by the combustion enginewaste heat and experiences a phase change to its gaseous state as theorganic Rankine cycle repeats. The presence of working fluid throughoutthe closed loop system ensures that the process is continuous as long assufficient heat energy is present at input port 106 to provide therequisite energy to heat the working fluid to the necessary temperature.See, for example, Langson U.S. Pat. No. 7,637,108 (“Power Compounder”)which is hereby incorporated by reference.

As a result of the transfer of waste heat energy from the combustionengine to the ORC system, these types of prior art ORC systems serve twofunctions. They convert this waste heat energy, which would otherwise belost, into productive power and they simultaneously provide abeneficial, and sometimes a necessary, cooling or condensation functionfor the combustion engine. In turn, the ORC system's shaft output powerhas been used in a variety of ways, such as to drive an electric powergenerator or to provide mechanical power to the combustion engine, apump, or some other mechanical apparatus.

ORC systems can extract as much useful heat energy as is practicablefrom one or more waste heat sources (often referred to as the “primemover”), but owing to various physical limitations they cannot convertall available waste heat to mechanical or electric power via theexpansion process discussed above. Similar in some respects to thecooling requirements of the prime mover, the ORC system requirespost-expansion cooling (condensation) of its working fluid prior torepressurization of the working fluid by the system pump and delivery ofthe working fluid to the heat exchanger. The heat energy lost in thiscondensation process, however, represents wasted energy which detractsfrom the overall efficiency of the system.

Some prior art combined prime mover/ORC engine applications haveutilized heat generated by the ORC condensation process in aconventional ORC system condenser while simultaneously providing power(electrical and/or mechanical) for various purposes. Combined heat andpower (“CHP”) ORC systems have typically fulfilled a secondary purposeby using a portion of the heat energy from the prime mover and/or heatenergy remaining in the post-expansion working fluid. FIG. 5 depicts aprior art ORC system including combustion engine heat energy output port501 and condenser heat energy output port 502.

In one prior art ORC application, residual heat extracted from adedicated ORC condenser during the cooling of post-expansion ORC workingfluid at condenser heat energy output port 502 is used to providedomestic hot water, radiant heating, or both. This process requires theuse of a conventional ORC condenser system well known in the art. Theenergy flow of such an application is depicted in the block diagram ofFIG. 6. Here, a heat generating engine 601 is operatively coupled toelectric generator 602 and provides waste heat energy 603 to the ORCsystem 604, which is operatively coupled to drive electric generator605. Heat energy from the prime mover 601 is delivered to heat energyoutput port 501 and, in some prior art systems, is extracted to (i) afirst heat energy input port 606 (such as for radiant heating) and (ii)a second heat energy input port 607 (such as for hot water heating). Inthose ORC systems known by the applicants, the utilization of residualheat from the post-expansion working fluid is intentionally extractedfrom the system but is not utilized for further system optimization ofthe prime mover or, for example, for heating a production material suchas microorganisms to generate biofuel.

BRIEF SUMMARY OF SOME ASPECTS OF DISCLOSURE

The applicants have invented apparatus, systems, and methods thatproductively utilize heat energy generated by ORC working fluidcondensation to produce fuel or other power or energy for use by theprime mover. In some embodiments, the prime mover can use the fuel,power, or energy to drive a prime mover.

In certain embodiments, the system includes: (i) a biogas generationsystem providing combustible biogas to fuel the prime mover; (ii) aprime mover that provides heat energy to drive an ORC engine; and (iii)an ORC engine that provides heat energy to drive the biogas generationsystem. In some embodiments, the biogas generation system utilizes ananaerobic digestion process which can utilize ORC heat energy tomaintain the temperature for the anaerobic process to take place.

In some embodiments, the prime mover may provide mechanical power todrive one or more electric generators. In some embodiments, suchgenerators can he connected to a power distribution grid.

In some applications, the biogas generation system can be co-locatedwith prime mover and ORC system(s) so that (i) one or more primemover(s) provide waste heat to drive one or more co-located ORCsystem(s), (ii) one or more ORC system(s) provides waste heat tomicroorganisms to drive the co-located biogas generation system, and(iii) resulting biogas can provide fuel for one or more co-located primemover(s). In some of these applications, one or more prime mover(s) andone or more ORC system(s) can simultaneously provide productive powerfor an of a wide variety of devices and applications, locally orotherwise. Alternatively or in addition, the ORC system(s) may providewaste heat to co-located heat consuming system(s) other than biogasgeneration system(s). In some applications, the prime mover may receivefuel from more than one source. For example, a prime mover may run onlocally-generated biogas during a portion of its operating schedule andanother fuel during other portions of its operating schedule. Such otherfuels may include but are not limited to stored biogas, biogas importedfrom other sources, other forms of combustible gasses, or alternatefuels (liquid, solid, or gaseous) suited to the requirements of theprime mover. In some applications, fuels from multiple sources may bemixed together and that mixture supplied to the prime mover. Thistechnique would allow the operator to control the composition of thefact and the exhaust emissions of the prime mover based in itsavailability and to maximize performance and cost efficiency of itsoperation.

In some instances, waste heat energy obtained from the exhaust gassesand/or cooling jacket water of the prime mover is provided to one ormore ORC system(s) which are operatively coupled to one or more separateelectrical generator(s) that are similarly connected to the commercialpower distribution grid. The heat coupling subsystem can comprise a heatexchanger which is operatively coupled to provide the requisitecondensation of ORC working fluid by transferring heat energy from saidfluid to one or more anaerobic digester tank(s). That heat energy canhelp optimize production of biogas from the anaerobic digestion processused to power the prime mover, and, when operated in concert with an ORCsystem also generating electric power, improve the efficiency of, andmaximize the economic benefit of, the combined system.

The prime mover of some embodiments can be any system, apparatus, orcombination of apparatus, that converts some or all of its input energyinto heat energy or waste heat energy in a form and quantity sufficientfor use by one or more ORC system(s). In some embodiments, the onlypurpose of the prime mover will be to generate heat for the ORCsystem(s). All heat energy sources co-located, compatible for use with,and utilized by one or more ORC system(s) fall within the scope of theterm “waste heat” for the purpose of this application.

In some systems, a prime mover can generate and deliver mechanical powerto an electric power generator in addition to providing waste heatenergy for the ORC system(s). In certain embodiments, a prime mover cansimultaneously generate more than one form of waste heat, including butnot limited to cooling water, hot exhaust gas, or radiated heat. Thewaste heat energy may be captured and provided to the ORC system in anypracticable manner, either directly or via one or more intermediate heatexchanger systems.

In some instances, one or more prime movers may provide waste heatenergy to one or more ORC systems. In some embodiments, a single heatexchanger may be employed for any ORC system, any prime mover, anysource of heat energy from each prime mover, or for more than one ORCsystem, prime mover, or heat energy source. These heat exchangers mayhave separate input ports and separate output ports for the energysource(s) or a single input and/or output port may be utilized for morethan one source.

In certain embodiments, one or more ORC system(s) operate with a closedloop refrigerant cycle to prevent intermixture of working fluid betweensystems. Similarly, in some instances one or more prime mover(s) operatewith a closed loop jacket water cooling system to prevent anyintermixture of jacket water between systems. In other embodiments, asingle exhaust gas heat recovery system is employed to recover wasteheat energy from more than one prime mover and provide such heat energyto more than one associated ORC system. In some embodiments, a heatrecovery system receives heat energy input from one or more sourcesand/or provides heat energy to more than one ORC system.

In some systems, one or more additional heat sources provide heat inputto the ORC system(s). For example, a portion of the biogas generated bythe anaerobic digestion process may be burned a separate boiler and usedto provide heat input to the ORC system(s) in addition to, or in lieuof, waste heat input from one or more prime mover(s).

in certain embodiments, a portion of the waste heat energy from theprime mover may be applied directly to the anaerobic digestion processwithout having been first applied to the ORC system(s). This can bebeneficial in the event that the anaerobic digestion heatingrequirements exceed the residual heat energy available from thepost-expansion working fluid in the ORC system(s).

In some applications, one or more ORC systems constitute the entirejacket water cooling system for the prime mover(s). In such cases, theORC systems may replace alternative prime mover cooling systems, whichconsume, rather than generate, power during operation and thereforeusually have a significant cost of operation in addition to their costof installation. Such power consuming dedicated prime mover coolingsystems typically have a significantly larger footprint than an ORCsystem; and therefore they may have additional physical spacerequirements at the generation facility. They may also generate noiseand unwanted environmental heat pollution as a consequence of operation.Employing one or more ORC system(s) in lieu of power consuming dedicatedprime mover cooling systems, which are net consumers of power under suchcircumstances, can be economically, physically, and environmentallybeneficial.

In some embodiments, the waste heat recovery system(s) include one ormore power generating system, which may be ORC system(s), and one ormore power receiving component(s), which may be but are not limited toelectric power generator(s), prime mover(s), pump(s), combustionengine(s), fan(s), turbine(s), compressor(s), and the like. Therotational mechanical power generated by the power generating system(s)is delivered to the power receiving components.

In some embodiments, the ORC system(s) provide a portion of the coolingsystem for the prime mover(s) and operate in conjunction with one ormore additional cooling system(s). In some embodiments, electric powergenerated by the ORC systems may be applied to the operation of saidadditional cooling systems for the prime mover as well as provideelectric power for other purposes at the site or elsewhere. This can beparticularly advantageous if, for example, the prime mover is configuredto solely provide mechanical power output and a commercial source ofelectric power is not readily available.

In some embodiments, one or more ORC system(s) may provide heat energyto one or more anaerobic digestion tanks or other anaerobic digestionstructure. In some instances, multiple ORC systems can provide heatenergy to a single anaerobic digestion tank. In some embodiments, theanaerobic digestion heating system includes the entire condensersubsystem for the ORC system(s). In other embodiments, the anaerobicdigestion heating system comprises a portion of the ORC condensersubsystem(s) in combination with one or more other condensing system(s)which may operate on a regular or intermittent basis dictated by anumber of factors including seasonal requirements. The ambientenvironmental conditions, the number of ORC systems and their ratings,and/or the number, configuration, location, or volume of the anaerobicdigestion tanks may each be factors in determining the configuration andoperation of the condenser portion of the ORC systems.

In some embodiments, the heat energy supplied by the ORC system to theanaerobic digestion process can reduce or even completely obviate theneed for a supplemental anaerobic digestion tank heating system. In someinstances, this can reduce or even eliminate the cost of installation,maintenance, and operation of such supplemental system, including costsassociated with electric power and/or other fuels which may havepreviously been consumed by its operation. In some cases, the ORC systemcan provide heat to the anaerobic digestion process in combination withone or more other heating systems, which can serve to reduce rather thaneliminate the attendant costs.

In some embodiments, the ORC system supplies all heat required by theanaerobic digestion system via the transfer of heat energy from the ORCprocess. In some embodiments, some or all of the electric powergenerated by the ORC system can be supplied to electrical heatingsystems to heat the anaerobic digestion tank(s). This heating can be inaddition to, or in lieu of, the direct transfer of heat energy from theORC system to the anaerobic digestion system and can vary based onfactors such as the availability of heat enemy and/or other electricalpower, heating requirements, and the like. In some embodiments, aportion of electric power output generated by the ORC system is suppliedto other components or systems operatively connected (eitherelectrically, mechanically, or thermally) to the combined ORC andanaerobic digestion system, including but not limited to other heatingsystems, cooling systems, fans, pumps, compressors, circulation systems,filtration equipment, stirring systems, and the like.

The foregoing is a brief summary of only some of the novel features,problem solutions, and advantages variously provided by the variousembodiments. It is to be understood that the scope of the invention isto be determined by the claims as issued and not by whether a claimaddresses an issue noted in the Background or provide a feature,solution, or advantage set forth in this Brief Summary. Further, thereare other novel features, solutions, and advantages disclosed in thisspecification; they will become apparent as this specification proceeds.

BRIEF DESCRIPTION OF THE DRAWINGS

Without limiting the invention to the features and embodiments depicted,certain aspects this disclosure, including the preferred embodiment, aredescribed in association with the appended figures in which;

FIG. 1 is a block diagram of a prior art ORC system used to convertwaste heat energy into electric power;

FIG. 2A is a block diagram of a heat coupling subsystem with heatexchangers to transfer heat energy from a closed loop system to ananaerobic digestion tank;

FIG. 2B is a block diagram of a single ORC system used to convert wasteheat energy into electric power while simultaneously providing heatenergy to a single anaerobic digestion tank that provides condensingfunctionality for the ORC system;

FIG. 2C is a block diagram of a single ORC system used to convert wasteheat energy into electric power While simultaneously providing heatenergy to a single anaerobic digestion tank that provides partialcondensing functionality for the ORC system, augmented by the presenceof a separate condenser;

FIG. 3 is a block diagram of multiple ORC systems simultaneouslydelivering heat energy to a single anaerobic digestion tank whileproviding condensing functionality for the ORC systems;

FIG. 4 is a block diagram of a single ORC system simultaneouslydelivering heat energy to a multiple anaerobic digestion tanks whileproviding condensing functionality for the ORC system;

FIG. 5 is a block diagram of a prior art ORC system used to convertwaste heat energy into electric power including heat extraction portsthat can be used to provide heat for other applications;

FIG. 6 is a block diagram of the energy flow in a prior art systemcomprising a prime mover, an ORC system used to convert waste heatenergy into electric power, and heat extraction ports for othernon-system applications;

FIG. 7 is a block diagram of the energy flow in a system comprising aprime mover, an ORC system used to convert waste heat energy intoelectric power, and heat extraction from the prime mover used to improvesystem efficiency;

FIG. 8 is a block diagram of the energy flow in a system comprising aprime mover, an ORC system used to convert waste heat energy intoelectric power, and heat extraction from the ORC system used to improvesystem efficiency;

FIG. 9 is a block diagram of the energy flow in a system comprising aprime mover, an ORC system used to convert waste heat energy intoelectric power, and heat extraction from the prime mover and from ORCsystem used to improve system efficiency; and

FIG. 10 is a block diagram of a single ORC system used to convert wasteheat energy into electric power while simultaneously providing heatenergy to a single anaerobic digestion tank that provides condensingfunctionality for the ORC system, including heat extraction ports thatcan be used to provide heat for other applications.

DETAILED DESCRIPTION OF THE PREFERRED AND OTHER EMBODIMENTS

The process of anaerobic digestion is well known in the art. Certainstrains of bacteria, in the absence of oxygen, are employed to breakdown, or digest, certain biodegradable material including food, yard, orother waste into combustible gasses consisting of methane, hydrogen, andother trace components, as well as a residual solid effluent. Thiseffluent, or sludge, contains ammonia, phosphorous, potassium, and othertrace materials and is beneficial to agriculture as a supplementalenrichment fertilizer for soil.

The anaerobic digestion process involves three basic stages involvingdifferent microorganisms, and the temperature of the cultures can play avery significant role in the efficiency of the digestion process.Mesophilic digestion, occurring at medium temperatures, can be appliedto discrete batches of biodegradable waste while thermophilic digestion,occurring at higher temperatures, may preferably be utilized on acontinuous basis. Although the anaerobic digestion microorganisms cansurvive within the range from below freezing to above 135° F. optimaldigestion occurs at 98° F. for mesophilic organisms and 130° F. forthermophilic organisms. Bacterial activity and therefore biogasproduction is significantly reduced at greater temperatures and declinesat a somewhat lesser rate at cooler temperatures. The requirement forheating of the cultures may vary over time (over the course of a singleday and, as seasons change, throughout the year) based on ambienttemperatures.

With reference now to FIG. 2A, a heat coupling subsystem 201 can be usedto transfer heat energy to the anaerobic digestion process whilemaintaining media isolation between a heat source and an anaerobicdigestion system in the heating tank 208, owing to potentially differentmedia requirements of the two systems. The heat coupling subsystem 201includes (i) an intermediate heat exchanger 204, (ii) an anaerobicdigestion tank heat exchanger 207 within, as part of the wall of, orotherwise in direct thermal communication with, the anaerobic digestiontank 208, (iv) pumping apparatus 209 between the tank heat exchanger 207and the intermediate heat exchanger 204, (v) operative coupling betweenthe various components described below, and (vi) secondary media (whichmay be the same as or different from the primary medium depending onsystem requirements) flowing within the isolated closed loop provided bythe tank-side (secondary) portion of the heat coupling subsystem 201 viathe input port 206 and the output port 205, the anaerobic digestion tankheat exchanger 207, and the pumping apparatus 209. Heat couplingsubsystem 201 may also include storage reservoirs (not shown) for aquantity of both the primary medium and the secondary medium asnecessary to insure that sufficient media is available for the properoperation of each closed loop systems on the primary and secondarysides.

The primary side of the intermediate heat exchanger 204 includes aprimary side input port 202 to receive the heated primary media (notshown) from the heat source, which may be an ORC system, a prime mover,or any other source of heat energy, a primary side heat exchangersection 204A, and a primary side output port 203. This flow providesheat energy from the ORC system for transfer to, and use by, theanaerobic digestion tank(s), e.g., 208. The heated primary media can beORC working fluid, water, a mixture of water and ethyl glycol, a mixtureof water and one or more other components, or any other fluid or gaseoussubstance compatible with the application and apparatus. The heatedprimary media passes through the primary side 204A of intermediate heatexchanger 204 and exits at primary side exit port 203. Heat energy fromthe heated primary media is transferred to the secondary side of theintermediate heat exchanger 204, through which a suitable secondarymedia (not shown) enters at secondary side input port 206, flows throughsecondary side heat exchanger section 204B, and exits at secondary sideoutput port 205. This heated secondary media then flows throughanaerobic digestion tank heat exchanger 207, where heat energy istransferred from the heated secondary media to the contents of anaerobicdigestion tank 208 before being pressurized by pumping apparatus 209 andreturned to secondary side of the intermediate heat exchanger 204 at thesecondary side input port 206.

With reference now to FIG. 2B, an ORC system, generally 200, utilizesthe heat coupling subsystem 201 within, as part of the wall of, orotherwise in direct thermal communication within anaerobic digestiontank 208 to provide cooling for the post-expansion working fluid exitingfrom the expander 102. The ORC working fluid exits the expander 102 andenters input port 202, travels through the heat coupling subsystem 201,and then exits the output port 203 and enters the system pump 105. Theheat coupling subsystem 201 and anaerobic digestion tank 208 thereforeprovide an integrated working fluid condensation and heat consumptionsystem. That is, the anaerobic digestion tank heat exchanger 207, whencoupled to the ORC system via intermediate heat exchanger 204 in themanner shown in FIG. 2A and described in detail above, comprise heatcoupling subsystem 201 which may be considered to function as a singleheat exchanger for the purposes of the ORC system. Analogous to theperformance of a transformer in an electrical system, heat couplingsubsystem 201 serves as a “thermal transformer” which transfers heatenergy from its primary (ORC) side to its secondary (tank) side whilemaintaining isolation between the separate media flowing in each closedloop. This provides the equivalent performance of a condenser known inthe prior art with significant improvements. This particular system isalso a production system, meaning that the heat coupling subsystem 201provides heat energy, via anaerobic digestion tank heat exchanger 207,directly for production and not for mere disposition of the heat aswaste. In this example, the anaerobic digestion tank heat exchanger 207directly heats the contents of the anaerobic digestion tank 208,yielding production of biogas. The temperature of the post-expansionworking fluid entering input port 202 should be about 125° F., which isnearly ideal for the purpose of supplying heat to a continuousmesophilic anaerobic digestion process including the heat energy lossesfrom an intervening intermediate heat exchanger.

Referring to both FIGS. 2A and 2B, in an embodiment utilizing anintermediate heat exchanger 204, less heat energy will be delivered tothe anaerobic digestion tank(s) than is provided to the primary side,i.e., through input port 202, of heat coupling subsystem 201 due to theunavoidable loss of heat energy during the heat transfer process fromthe primary medium to the secondary medium via intermediate heatexchanger 204. However, for applications with reduced anaerobicdigestion heating requirements, such as mesophilic digestion processes,this loss of heat energy can be beneficial and can eliminate therequirement for a dedicated supplemental condensing apparatus. Thismethod may be applied to any configuration of the anaerobic digestionheating apparatus.

With reference now to FIG. 2C, the structure and operation of the systemis identical to that of FIG. 2B with the addition of an ORC condensersubsystem 104 between the input port 202 and the outlet port 203.Post-expansion ORC working fluid can thus travel through either or both(i) the condenser subsystem 104 and (ii) the heat coupling subsystem 201associated with the anaerobic digestion tank 208. This embodiment may beused when insufficient condensing capacity might be provided by theanaerobic digestion tank 208 or during periods of ORC operation when theanaerobic digestion tank 208 is not in service.

With reference now to FIG. 3, a series of ORC systems 301, 302, 303 arecombined to provide heat energy to an anaerobic digestion tank 308.Although three ORC systems are depicted, any number of ORC systems canbe included to provide the desired level of heat transfer to theanaerobic digestion tank 308. This embodiment may be particularlyadvantageous for large anaerobic digestion facilities in order tomaintain a uniform temperature throughout a large volume anaerobicdigestion tank 308. Since the temperature of the medium circulatingwithin the anaerobic digestion heating system can be higher at its pointof entry into the tank and generally lowest at its point of exit as theheat energy is transferred to the contents of the tank, the introductionof several independent ORC systems, e.g., 301, 302, 303 at differentlocations in the anaerobic tank 308 can provide for a more evendistribution of heat and corresponding uniform temperature than would bepossible from a single source.

The same or similar result may be achieved by a single ORC system (notshown) using a specially designed manifold system (not shown) havingmultiple heat coupling subsystems 201. For larger digestion tanks,however, the finite heat energy available from a single ORC system maybe insufficient to maintain the temperature of the tank contentsuniformly at its desired, and in some instances, optimal value. Anyconfiguration of heat coupling subsystems 201 may be employed to provideoptimal results.

In order to provide the desired results, the geometry and configurationof an anaerobic digestion tank heat exchanger 201 used to simultaneouslyheat the contents of the anaerobic digestion tank(s) and providecondensation of the post-expansion working fluid can be designed andimplemented in view of the desired performance of both subsystems. Inone embodiment, the heated medium (the post-expansion working fluid)flowing within the anaerobic digestion tank heat exchanger 201 maydirectly circulate within a series of interconnected pipes and/ormanifolds (not shown) inside the anaerobic digestion tank(s). Thesestructures can be essentially planar with media flows in a single plane(neglecting the thickness of the components) or may be more threedimensional with heated medium flows in two or more planes. Theconfiguration of the anaerobic digestion tank heat exchanger 201 may bedesigned with, as shown in FIGS. 2B and 2C, a single input port 202 andoutput port 203 or may be configured with, as shown in FIG. 3, multipleinput ports 202 and output ports 203 to provide a more uniformdistribution of heat throughout the anaerobic digestion tank 308.Further, the interconnected pipes and/or manifolds may include a seriesof valves that permit control and redirection of the heated medium tovarious regions of the anaerobic digestion tank 308 as may be desired toachieve the preferred distribution of heat. In another embodiment, theheated medium may circulate through sealed channels embedded in thewalls of the anaerobic digestion tank(s), thereby heating the contentsof the tank at its interior boundaries or side wall(s).

With reference now to FIG. 4, a single ORC system 400 may be used toprovide heat energy to more than one anaerobic digestion tank (notshown) via multiple heat coupling subsystems 401, 402, and 403. In thisembodiment, the available heat energy from post-expansion working fluidfrom an ORC system 400 is distributed to anaerobic digestion tank heatexchangers (not shown) in each of three discrete anaerobic digestiontanks (not shown) via heat coupling subsystems 401, 402, and 403. Eachof these heat coupling subsystems 401, 402, 403 may be comparable toheat coupling subsystem 201 shown in FIG. 2A. The specific distributionof post-expansion working fluid provided to each heat coupling subsystem401, 402, 403 can be controlled, varying it as needed to allocate theavailable heat energy among the several tanks. In some instances, thismethod can be well suited for smaller tanks, systems with reducedrequirements for anaerobic digestion heating, or lower temperaturemesophilic batch processing, particularly where not all tanks are insimultaneous use. Although three tanks are referenced here, any numberof tanks are envisioned that provide the requisite performance.

These combined ORC and anaerobic digestion systems are distinguishedfrom known prior combined heat and power systems in that the priortechnology merely siphons some portion of heat energy from ports addedto known ORC systems. The known prior art does not teach, for example,the replacement of ORC condenser systems, in whole or in part, with analternate system including one that simultaneously provides, via oneheat coupling subsystem: (i) heating directly to a heat consumingprocess which provides some beneficent function and (ii) an equivalentcooling and condensation function for the ORC working fluid primarymedia, which may be heated post-expansion working fluid from the ORC. Inthis regard, known prior art ORC systems typically require significantelectric power to drive fans or an equivalent cooling system. Theeconomic advantage of generating power from waste heat energy is greatlyreduced when a lame portion of the generated power is consumed by thesystem's internal requirements (sometimes referred to as the “parasiticload”). The combined ORC and anaerobic digestion system thus provides adouble economic advantage; not only is the requisite cooling providedfor the primary media, which in the case of an ORC will be heatedpost-expansion working fluid, without additional electric powerconsumption, but the electric power normally required to maintain theanaerobic digestion tanks at the optimal temperature is no longerrequired due to the transfer of heat energy from the companion ORCsystem. While the known prior art requires electric power tosimultaneously cool the ORC media and heat the anaerobic digestiontanks, the combined ORC and anaerobic digestion system reduces oreliminates both requirements for electric power by transferring unwantedheat energy directly via heat coupling subsystem 201 from the ORC systemto the anaerobic digestion system. As a result, the net electric powergenerated by the combined ORC and anaerobic digestion system issignificantly greater than in the present art, providing greatereconomic benefit while conserving resources necessary to produceelectric power.

In some embodiments of the present application, anaerobicdigestion-based biogas power generation systems can be enhanced byintegrating the functions of an ORC waste heat energy generation systemwith the biogas-burning prime mover and the anaerobic digestion processwhich generates the biogas for the prime mover. Both the heat input andheat output of the ORC system can be coupled to other components withinthe overall system. Unlike the known prior art, which does not integrateall three subsystems into a single optimized energy conversion system,some embodiments of the present application provide for increased andpossibly maximum efficiency by utilizing more and possibly all availableheat energy within the system to a greater, and possibly the greatest,extent practicable.

In certain embodiments, no heat energy is intentionally dissipated orredirected to any non-system application. In certain instances, as someor all of the lowest grade residual waste heat energy remaining aftertwo stages of electric power generation is returned to enhance, and insome instances optimize, the production of fuel for the primary electricpower generation process, the system forms a novel and more effectivethree stage closed-energy-loop.

More specifically, the novel combined prime mover, ORC, and anaerobicdigestion system taught herein uniquely allows for each of the threecomponent systems to provide operational benefits of the other two.Specifically, the anaerobic digestion system can, in certainembodiments, be the anaerobic digestion system offered by Harvest Poweras described above. In certain embodiments, the prime mover(s), whichcan be the Jenbacher 312 or 316 internal combustion engines alsodescribed above, are faded by biogas produced by the anaerobic digestionprocess and cooled, in whole or in part, by one or more ORC system(s)which remove undesired waste heat energy and convert it to usefulmechanical and/or electrical power. In this manner, the ORC system(s),which in certain embodiments can be Series 4000 Green Machine ORCsystem(s) offered by ElectraTherm. Inc. of Reno, Nev., receive theirinput energy in the form of waste heat from the prime mover(s) andprovide post-expansion heat energy to the anaerobic digestion process toenhance the production of biogas fuel for the prime mover(s).Additionally, the heat energy from the ORC that is absorbed by theanaerobic digestion process system provides the necessary coolingcondensation of post-expansion ORC working fluid, obviating the need fora separate ORC condenser and the attendant cost of operation. As each ofthe three component system enhance the operation of the other two, allavailable heat energy is utilized to the greatest extent possible andthe need for additional energy, particularly electrical energy, toprovide cooling and/or heating as in the present art is minimized oreliminated.

In one embodiment depicted in FIG. 7, the prime mover 601 cansimultaneously contribute heat energy and/or waste heat energy 603 tothe ORC system 604 and heat energy 702 to the anaerobic digestion tank701, which provides the biogas fuel for the prime mover 601.

In an embodiment depicted in FIG. 8, the ORC system 604 can obtain itsheat input from the waste heat energy 603 of prime mover 601 and deliverits own waste heat energy 801 to the anaerobic digestion process. Heatenergy flow 801 may he provided from the post-expansion working fluid toanaerobic digestion tank 701.

In an embodiments depicted in FIG. 9, both the prime mover 601 and theORC system 604 provide heat energy to anaerobic digestion tank 701 asdepicted in FIG. 9 via heat flows 702 and 801, respectively.

In addition to the heat energy being transferred from the primary media(which in some embodiments may be post-expansion ORC working fluid) tothe anaerobic digestion process to increase the efficiency of theoverall system, heat energy may also be extracted for other purposes.With reference now to FIG. 10, a prime mover (not shown in FIG. 10) canprovide heated prime mover media to the heat exchanger 101 of an ORCsystem 1000 and to a prime mover heat energy output port 501.Post-expansion working fluid heat energy can be provided to theanaerobic digestion tank heat exchanger 201 and to an output port 1001;and post-anaerobic digestion tank heat exchanger heat energy can beprovided to output port 1002. Any combination of these ports may beutilized to provide heat energy for one or more purposes not related tothe operation of the CHP system.

In addition to anaerobic digestion systems, any application benefittingfrom significant heat enemy may be similarly integrated with an ORCsystem as a heat receiving system with condensation capacity in themanner taught herein. The anaerobic digestion tank(s) function as asingle subsystem providing combined working fluid condensation and theconsumption of heat energy for beneficent use. As with the heating ofanaerobic digestion tank(s), any application in which coupled heatenergy from the primary media may replace the generation of heat energyvia the consumption of electric power will operate with greaterefficiency and economic benefit and may serve as a heat receiving systemwith condensation capacity. Such applications may include but are notlimited to the heating of water in swimming pools, preheating water forboiler systems, space heating, industrial or large scale domestic hotwater systems, combined heat and power systems, and the like. As aresult, these systems will also provide the dual benefit of providingheat energy normally produced by electric power while simultaneouslyeliminating the need for a separate ORC cooling and condensing system inthe present art.

In some embodiments where insufficient cooling and condensationfunctionality may be available from the anaerobic digestion system forproper operation of the ORC, a supplemental or alternate system may berequired if it is desirable to run the ORC. In some embodiments, the ORCmay serve as a primary cooling system for the prime mover(s). Thedescription of this invention is intended to be enabling and not it willbe evident to those skilled in the art that numerous combinations of theembodiments described above may be implemented together as well asseparately, and all such combinations constitute embodiments effectivelydescribed herein.

What is claimed is:
 1. A method of energy conversion and fuel generationcomprising: A. with a fuel consuming heat source, generating at least afirst portion of source waste heat and a second portion of source wasteheat; B. with an ORC system, converting energy in the first portion ofsource waste heat into ORC power and ORC waste heat; and C. with a heatsource fuel generation system including an anaerobic digestioncomponent, generating heat source fuel using the ORC waste heat.
 2. Themethod of claim 1 comprising an additional step of using the secondportion of source waste heat with the heat source fuel generation systemto generate heat source fuel.
 3. The method of claim 1 wherein the heatsource fuel generation system includes a biogas generation component. 4.The method of claim 2 wherein the heat source fuel generation systemincludes a biogas generation component.
 5. The method of claim 1 whereinthe ORC system comprises an electric generator and the ORC power iselectric power.
 6. The method of claim 2 wherein the ORC systemcomprises an electric generator and the ORC power is electric power. 7.The method of claim 1 wherein the ORC power is delivered to at least oneof any of the heat source, an electric generator, a prime mover, a pump,a combustion engine, a fan, a turbine, or a compressor.
 8. The method ofclaim 2 wherein the ORC power is delivered to at least one of any of theheat source, an electric generator, a prime mover, a pump, a combustionengine, a fan, a turbine, or a compressor.
 9. The method of claim 1further comprising a step of communicating the heat source fuel to theheat source for consumption.
 10. The method of claim 2 furthercomprising a step of communicating the heat source fuel to the heatsource for consumption.
 11. The method of claim 1 wherein the ORC systemcomprises a screw expander.
 12. The method of claim 2 wherein the ORCsystem comprises a screw expander.
 13. A heat coupling apparatus for anenergy conversion and fuel generation system, the apparatus comprising:A. an input port in heated primary media receiving communication with asource of heat energy; B. a closed loop thermal communication circuitcomprising a circulating secondary media (i) in heat energy receivingcommunication with the heated primary media; (ii) in heat energydelivery communication with contents of at least one biogas-producinganaerobic digestion tank; and (iii) in flow communication with a pumpingapparatus; and C. an output port in primary media sending communicationwith the source of heat energy.
 14. The apparatus of claim 13 wherein atleast a portion of the biogas produced by the contents of the at leastone anaerobic digestion tank is communicated to the source of heatenergy.
 15. The apparatus of claim 13 further comprising one or morestorage reservoirs for the primary media, the secondary media, or both.16. The apparatus of claim 13 wherein the source of heat energy is anORC system and the heated primary media is ORC working fluid.
 17. Theapparatus of claim 13 wherein at least one of the primary media orsecondary media comprise an organic refrigerant.
 18. An energyconversion and fuel generation system comprising: A. a prime moverconfigured to burn biogas; B. an ORC system configured to convert primemover waste heat into ORC power and ORC waste heat; and C. an anaerobicdigestion process configured to use the ORC waste heat to produce biogasfor combustion by the prime mover.
 19. The system of claim 18 whereinthe ORC power is electric power.
 20. The system of claim 18 wherein theprime mover is a first prime mover and the ORC power is delivered to atleast one of any of an electric generator, the first prime mover, asecond prime mover, a pump, a combustion engine, a fan, a turbine, or acompressor.